First, let me be clear that I am not attacking the OPs of these questions. I think this is an important issue that needs to be brought up soon in the beta process.
A couple sample questions to look at:
Both of these questions actually mix languages (Spanglish?) in their titles (and the second one in the actual question, too). I think this needs to be discouraged.
Note that I'm not arguing against allowing Spanish and English questions (or answers), I'm arguing against randomly mixing the two.
Let me consider the first one first:
The proper phrasing (and I've already made this edit), I believe, is "vaso de agua" or "vaso con agua"? Which is correct? or "vaso de agua" o "vaso con agua"? Cuál es correcto? The addition of quotation marks is necessary in either case, I believe. I hope what I'm pointing out is clear here... The entire question should be in English or in Spanish (the exception being the bits in quotes, which are what the question is about)
The second one may be a bit of a special case. (Although I don't think it actually is).
I believe the proper phrasing for the second question should be: Preterit of ser and ir. There's no need to mix languages here, either unless the OP is actually asking about subtlties in the Spanish pretérito tense that don't exist in the English preterit tense. But even then, the question itself still needs to be changed:
How did the verbs ser and ir evolve to have the same conjugation in the pretérito (and also in the imperfecto and futuro of subjuntivo)? And why do their forms in pretérito begin with fu-?
futuro of subjuntivo just sounds sloppy to me. It should be futuro de subjuntivo if it actually makes sense to say this in Spanish. More likely future subjunctive is the proper phrase here, since the rest of the question (except for verb tense names) is in English.
I hope that my edit on the first question is pretty uncontroversial, but if not, please express your dissenting opinions here. On the second one, I think we need to decide what actually makes sense. Is there a case to be made for expressing verb tenses in Spanish for the sake of clarity, even when the question is otherwise in English? And if so, does this question match that case?